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Cisco VISM Installation and Configuration Guide
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter3 VISM Functional Description
Call Control Function
VISM supports up to eleven domain names and each domain name can have up to eight internal and eight
external IP addresses.
Note The external DNS can have up to eight internal IP addresses only.
The interface between the call agent and other call agents is either Signaling System 7 (SS7) or a Cisco
extended ISDN User Part (C-ISUP).
Connection Model
SGCP and MGCP gateway call control protocols assume a connection model where the basic constructs
are connections and endpoints. Figure 3-11 shows a basic connection model.
Figure3-11 Connection Model
Connections are grouped into calls. One or more connect ions can be long to th e same c all. Several
connections, that may or may not belong to the same call, can terminate in the same endpoint.
The SGCP consists of the following commands:
•Notification request—Used by the call agent. Requests the gateway to send notifications upon the
occurrence of specified events in an endpoint.
•Notify Messages—Used by the gateway. Sends a list of observed events to the call agent.
•Create connection—Used by the call agent. Sets up a new connection at the gateway.
•Modify connection—Used by the call agent. Modifies a gateway’s view of a connectio n.
•Delete connection—Used by the call agent. Terminates a connection.
The MGCP extends SGCP to include the following commands:
•Audit endpoint—Used by the call agent. Audits information related to a given endpoin t.
•Audit connection—Used by the call agent. Audits information related to a given connection.
•Restart in progress —Used by the gateway (VISM). Signals that an endpoint (or a group of
endpoints) is brought into or taken out of service.
•Audit gateway—Used by the call agent. Identifies the status of the gateway.
•Audit line—Used by the call agent. Identifies the status of a given line.
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3
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Connection 1
Connection 2
Connection 3
Call 1
endpoin
ts
Call 2
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